Re: [PATCH] drm/xe/xe_late_bind_fw: Initialize uval variable in xe_late_bind_fw_num_fans()

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Thu, Oct 02, 2025 at 06:26:48AM +0530, mallesh.koujalagi@intel.com wrote:
> From: Mallesh Koujalagi <mallesh.koujalagi@intel.com>
> 
> Initialize the uval variable to 0 in xe_late_bind_fw_num_fans() to fix
> a potential use of uninitialized variable warning and ensure predictable
> behavior.
> 
> The variable is passed by reference to xe_pcode_read() which should
> populate it on success, but initializing it to 0 provides a safe
> default value and follows kernel coding best practices.
> 
> v2:
> - uval = 0 which serves as both a safe default and the fallback
>   value when the pcode read operation fails.
> 
> v3:
> - Handle MMIO failure (Rodrigo)
> - The function should probably return the error and make the uval as
>   pointer-argument, like the pcode_read.
> - Change the caller of this function to propagate the error
>   upwards if mmio failed.
> 
> Fixes: 45832bf9c10f3 ("drm/xe/xe_late_bind_fw: Initialize late binding firmware")
> Signed-off-by: Mallesh Koujalagi <mallesh.koujalagi@intel.com>

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

and pushing soon

> ---
>  drivers/gpu/drm/xe/xe_late_bind_fw.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_late_bind_fw.c b/drivers/gpu/drm/xe/xe_late_bind_fw.c
> index 8f5082e689dc..768442ca7da6 100644
> --- a/drivers/gpu/drm/xe/xe_late_bind_fw.c
> +++ b/drivers/gpu/drm/xe/xe_late_bind_fw.c
> @@ -184,17 +184,13 @@ static const char *xe_late_bind_parse_status(uint32_t status)
>  	}
>  }
>  
> -static int xe_late_bind_fw_num_fans(struct xe_late_bind *late_bind)
> +static int xe_late_bind_fw_num_fans(struct xe_late_bind *late_bind, u32 *num_fans)
>  {
>  	struct xe_device *xe = late_bind_to_xe(late_bind);
>  	struct xe_tile *root_tile = xe_device_get_root_tile(xe);
> -	u32 uval;
>  
> -	if (!xe_pcode_read(root_tile,
> -			   PCODE_MBOX(FAN_SPEED_CONTROL, FSC_READ_NUM_FANS, 0), &uval, NULL))
> -		return uval;
> -	else
> -		return 0;
> +	return xe_pcode_read(root_tile,
> +			     PCODE_MBOX(FAN_SPEED_CONTROL, FSC_READ_NUM_FANS, 0), num_fans, NULL);
>  }
>  
>  void xe_late_bind_wait_for_worker_completion(struct xe_late_bind *late_bind)
> @@ -314,7 +310,11 @@ static int __xe_late_bind_fw_init(struct xe_late_bind *late_bind, u32 fw_id)
>  	lb_fw->flags &= ~INTEL_LB_FLAG_IS_PERSISTENT;
>  
>  	if (lb_fw->type == INTEL_LB_TYPE_FAN_CONTROL) {
> -		num_fans = xe_late_bind_fw_num_fans(late_bind);
> +		ret = xe_late_bind_fw_num_fans(late_bind, &num_fans);
> +		if (ret) {
> +			drm_dbg(&xe->drm, "Failed to read number of fans: %d\n", ret);
> +			return 0; /* Not a fatal error, continue without fan control */
> +		}
>  		drm_dbg(&xe->drm, "Number of Fans: %d\n", num_fans);
>  		if (!num_fans)
>  			return 0;
> -- 
> 2.43.0
>